<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        
    </style>
</head>
<body>
    
</body>
<script>
    
    // NaN和任何数据都不相等，包括自身
    console.log( undefined + 1 );
    console.log( undefined + 1 === NaN );
    console.log( NaN === NaN );

    console.log( isNaN( NaN ) )
    console.log( isNaN( 123 ) )
    
    console.log( isNaN( "hello" ) )
    console.log( isNaN( "123124" ) )

    console.log( isNaN( "123a124" ) )

    // 隐式类型转换：其他转数值

</script>
</html>